The field of application of tubular films that have, for example, an olefin homo- or copolymer layer such as a polyethylene (PE) layer and a polyamide (PA) layer, for example, is very large. Some of the areas where they are used are, apart from the packaging industry, the tube lining system for pipe renovation, particularly trenchless sewage pipe renovation or pressure pipe renovation. In trenchless sewage pipe renovation, it is for example known from the glass fiber tube liner system with UV or steam curing that a thick-walled, high-density PE film (HDPE—high density polyethylene) is introduced first as sliding film—mostly in the cross-section form of a semicircle—and placed tightly against the pipe's inner wall. Afterwards, a flexible insertion tube developed as tubular film is drawn in (drawing-in process), in which case the insertion tube slides over the sliding film. On the one hand, this protects the insertion tube from damage caused by the pipe's inner wall or objects inside the pipe and, on the other hand, this significantly lowers the friction between insertion tube and sliding film, thus facilitating the drawing in of the insertion tube.
In the glass fiber pipe liner system with UV- or steam curing, such an insertion tube (tube liner) has typically an outer hose developed as a tubular film (outer tubular film) and an inner hose developed as tubular film (inner tubular film). Between them, a carrier material (e.g. glass fibers) impregnated with reactive plastic resin has been built in. Some of the reactive plastic resins that can be used are, for example, commercially available UP resins (polyester or unsaturated polyester resins), VE resins (vinyl ester resins) or EP resins (epoxy resins). In UP or VE resins, their curing can be done with the help of photo initiators, but the curing can also take with heat. In the pipe, the insertion tube is inflated from the inside by compressed air directed against the mechanically stable inner tubular film until the latter makes tight contact with the pipe's inner wall or sliding film in order to subsequently cure the resin with UV light from a UV light source being moved slowly through the interior of the inflated insertion tube, for example. Depending on the kind of embodiment of the inner tubular film of the insertion tube, it stays inside the pipe or is pulled out and removed.
To prevent undesired, premature curing of the plastic resin before introduction into the pipe to be renovated (particularly during storage), it is necessary for the outer tubular film of the insertion tube to have or consist of a protective layer that prevents a premature exposure of the resin to UV radiation or shorter-wave radiation of visible light, which would cause premature hardening of the resin. The inner tubular film of such an insertion tube must, however, be highly permeable to UV radiation and shorter-wave radiation of visible light. This makes the curing process possible, which is done in the tube liner inflated inside the pipe by a radiation source being pulled along the inner side of the tube liner, i.e. inside the inner tubular film.
Instead of the sliding film described above, a preliner (also known as preliner film) is introduced into the pipe to be renovated—especially in the synthetic fiber tube liner system with warm water or steam curing. A preliner, which typically consists of PE having a high density (HDPE—high density polyethylene), is a thick-walled film that lines the pipe fully and also prevents the tube liner from making direct contact with pipe's inner wall. To accomplish this, the preliner is placed tightly against the inner wall of the pipe and then the pipe liner is drawn into the pipe (drawing-in process) or inverted (inversion process). For example, the preliner prevents the plastic resin of the tube liner from gluing to the wall of the sewage pipe and the still uncured resin from making contact with dirt and water. Furthermore, the preliner film also prevents the resin from escaping to the sewage pipe renovation system and contaminating the soil and groundwater. The preliner film also protects inlets from penetrating excessive resin so no resin plugs and obstructions can form. Additionally, during the drawing-in process, a preliner assumes a similar function to reduce sliding friction as the sliding films described above for the tube liner to be drawn in. In this case, low coefficients of friction between sliding film or preliner and the outer film of the tube liner are essential. As a result of this, during drawing into the pipe, the insertion tube or tube liner is not damaged by the pipe's inner wall or objects inside the pipe and, on the other hand, the friction between tube liner and sliding film or preliner remains very low and facilitates the drawing in of the pipe liner.
It is known from state of the art to laminate both the outer tubular film and inner tubular film on the side facing the resin-impregnated carrier material with a nonwoven. In EP 1 180 225 B1, the main objective is the lamination of the outer tubular film, although lamination of the inner tubular film is mentioned. Lamination with a nonwoven layer has the advantage of facilitating the bonding of the corresponding tubular film to the resin-impregnated carrier layer, since the resin penetrates into the nonwoven layer and thereby prevents a displacement of the tubular film towards the carrier layer. Once the resin has cured, bonding to the nonwoven material is very strong and virtually impossible to separate. Also, this boosts the stability of the corresponding tubular film and a more uniform expansion when raising the tube liner inside the pipe to be renovated is made possible.
EP 1 180 225 B1 mentioned above also describes, as part of the manufacturing of the nonwoven laminated tubular film, the bonding of the border areas of two film bands running parallel to one another with the already previously laminated nonwoven. These border areas are not laminated because otherwise a bonding would not be possible.
EP 2 573 442 A1 likewise describes a bonding along a longitudinal seam, in this case for an inner tubular film laminated with a nonwoven.
The bonding or connection points are a disadvantage in the tubular flat films known because the places where they lack a nonwoven layer are less stable. Thus, a tubular or sealed or bonded flat film can open directly on the sealing seam or in close proximity to it because when a flat film is sealed to become tube shaped, the film thins out in the sealing area, but gets thicker in other areas.